Prolactin bioactivity and the duration of lactational amenorrhea

In our population, only half of fully nursing women remain amenorrheic 6 months postpartum. The other half recover their menstrual cycles between 90-180 days postpartum in spite of a high suckling frequency and elevated immunoreactive PRL (IR-PRL) concentrations. To further investigate the association of PRL with the recovery of ovarian function, we compared PRL bioactivity (BIO-PRL) 3-4 months postpartum in fully nursing amenorrheic women who subsequently experienced long (> 180 days; n = 5) or short (< 180 days; n = 5) lactational amenorrhea. In the present study, BIO-PRL in plasma was measured by the Nb2 lymphoma cell assay in samples taken before and 30 min after a suckling episode at 0800, 1600 and 2400 h. Women in the long amenorrhea group had higher overall mean BIO-PRL (mean +/- SE, 129.9 +/- 12.1 micrograms/L) than nursing women in the short amenorrhea group (66.6 +/- 5.2 micrograms/L; P < 0.05). Mean basal values were similar, but the women in the long amenorrhea group had more BIO-PRL in response to suckling (160.1 +/- 4.0 vs. 71.9 +/- 6.7 micrograms/L; P < 0.05). Compared with their respective basal values, nursing women in the long amenorrhea group demonstrated increased BIO-PRL in response to suckling, whereas the other group did not. The relationships between BIO-PRL and IR-PRL were similar in the two groups of nursing women before suckling. However, after suckling, the long amenorrhea group had significantly higher BIO-PRL levels than IR-PRL levels (P < 0.05, by likelihood test) than the short amenorrhea group. This suggests that suckling differentially changes in each group either the composition of PRL present or substances that may modify the bioactivity of PRL in plasma.     

Maternal nutritional status is inversely associated with lactational amenorrhea in Sub-Saharan Africa: results from demographic and health surveys II and III

Breast-feeding is positively associated with the duration of postpartum amenorrhea; thus it is a major determinant of fertility in countries where effective contraceptive methods are not widely available. The objective of these analyses was to examine the association between maternal nutritional status and lactational amenorrhea (LA) among breast-feeding women. Women who were not pregnant, who were breast-feeding, who were not using hormonal contraceptives and who had a child 相似文献   

Observation of proliferative capacity of rat salivary gland cells

Nursing interventions to enhance breastfeeding affect the health of mothers and babies. Fatigue may interfere with breastfeeding, so interventions minimizing fatigue are important. This repeated measures study of 20 postpartum women investigated the relative efficacy of one intervention, promoting use of the side-lying position. Using the Modified Fatigue Symptoms Checklist, fatigue was measured after breastfeeding in two positions. In mothers who had vaginal deliveries (n = 14), significantly less fatigue was reported following nursing in the side-lying versus the sitting position. Instruction regarding restfulness of the side-lying position should be considered as part of routine postpartum or home health nursing care.     

An event recorder for infant feeding research

An Event Recorder program was developed for the HP 48 calculator to record the durational events associated with breastfeeding behavior. The Event Recorder menu structure is flexible and allows for the recording of response variables such as menstrual history and fertility symptoms. A Windows program was written in Visual C++ to give a graphical representation of the time-series data and to extract useful measures of breastfeeding activity from the raw data for each 24-h day postpartum. These time varying covariates include the mean and median bout length, median interbout interval, breastfeeding frequency and total 24-h suckling duration. The HP 48 calculator has proven to be a robust instrument for the self-recording of breastfeeding data collected as part of a prospective study on the factors that maintain postpartum amenorrhea. We have found also that the behavioral data collected are easily transferred electronically each month when our field workers make home visits.     

Suckling-induced inhibition of luteinizing hormone secretion and follicular development in the early postpartum sow

The endocrine basis of lactational anestrus, the causes of reproductive dysfunction after early weaning, and the relationships among LH, FSH, and prolactin (PRL) secretion and follicular development were evaluated in sows weaned 6 h after farrowing (zero-weaned, n = 8) and in normally lactating sows (n = 9). An irregular, high-frequency episodic-type pattern of LH secretion was present in the early postpartum period, irrespective of treatment, and in a proportion of sows this pattern was associated with a marked elevation of baseline LH concentrations. This pattern of LH secretion was maintained in the zero-weaned sows but LH secretion was inhibited in lactating sows, resulting in a difference (p < 0.05) in mean plasma LH between groups 72-78 h postpartum. There were no differences in FSH between groups in any period of sampling. Variable but elevated plasma PRL was observed in suckled sows but declined (p < 0.05) to basal levels within 12 h of zero-weaning. Follicular development measured at laparotomy or slaughter 96 h postpartum was greater (p < 0.05) in zero-weaned than in control sows. The development of lactational anestrus in the sow therefore requires suckling-induced inhibition of LH secretion by 78 h postpartum. This inhibition of LH release does not appear to be causally related to short-term changes in PRL secretion.     

Does early supplementation affect long-term breastfeeding?

The purpose of this secondary data analysis from two different samples was to examine the effect of early supplementation with manufactured milks on breastfeeding status at 20 weeks postpartum in mothers of healthy term infants. In two convenience samples of 120 and 223, respectively, breastfeeding mothers were followed up for 20 weeks postpartum or until weaning occurred. The breastfeeding rate at 20 weeks postpartum was significantly greater for mothers who reported feeding exclusively mother's milk the second week after delivery compared with mothers who breastfed and simultaneously supplemented with manufactured infant milks. Of the mothers in samples one and two who exclusively fed human milk during week 2 postpartum, 63.0% and 59.7%, respectively, were still breastfeeding at week 20, compared with 28.1% and 24.2%, respectively, who supplemented with artificial milks. There was no significant difference between these two groups of mothers and their intended duration of breastfeeding. Early introduction of supplemental bottles of artificial milks is associated with a decrease in the amount of human milk the infant receives as well as with early weaning.     

The basal concentration and characteristics of the diurnal secretory rate of prolactin in women with primary hypothyroidism]

Basal concentration was measured of prolactin (PRL) as were its diurnal fluctuations in blood depending on the clinical association of primary hypothyrosis (PH) with lactorrhea-amenorrhea, lactorrhea only or lactorrhea associated with disturbances in menstrual and reproductive functions that differ from those in amenorrhea, and without such disturbances. Patients with lactorrhea-amenorrhea syndrome present with continual hyperprolactinemia and no physiological diurnal rythm of PRL secretion. In patients presenting without amenorrhea, and basal hyperprolactinemia, lactorrhea and disordered menses result from transitory "night-time" hyperprolactinemia. PH patients who do not present with lactorrhea and disordered menstrual and reproductive function show physiological diurnal rythm of PRL secretion, with its parameters corresponding to those in healthy women. The development of hyperprolactinemia in PH is not age-related; neither is it associated with severity of hypothyrosis.     

Prolactin and thyrotropin responses to thyrotropin-releasing hormone in patients with secondary amenorrhea: the effect of bromocriptine

Prolactin (PRL) and thyrotropin (TSH) responses to a 200 mug intravenous thyrotropin-releasing hormone (TRH) bolus were measured by radioimmunoassay in 11 women with hyperprolactinemic amenorrhea and 9 with normoprolactinemic amenorrhea. In all cases, the tests were carried out under basal conditions and repeated during bromocriptine treatment. In women whose basal PRL level was normal; TRH caused a maximal PRL increment of 85 +/- 25.2 mug/l (mean +/- SE), while those women whose basal PRL level was raised showed a smaller increase (5.2 +/- 11.9 mug/l) (P=0.02). The peak levels were not significantly different in these two groups (95.0 +/- 26.7 and 134.6 +/- 35.9 mug/l) (P is greater than 0.1). During bromocriptine treatment, the raised PRL levels decreased in all cases, but levels over 30 mug/l remained in 3 patients, one of whom turned out to have a pituitary tumor. Prolactin responses to TRH were markedly inhibited in normoprolactinemic patients by the dose of bromocriptine used. The mean maximal net increase of PRL was 2.0 +/- 0.9 mug/l in normoprolactinemic patients and 11.0 +/- 8.1 mug/l in hyperprolactinemic patients taking bromocriptine. After TRH stimulation during bromocriptine, the peak PRL levels in hyperprolactinemic patients were higher (32.7 +/- 10.5 mug/l) than in normoprolactinemic patients (7.2 +/- 1.5 mug/l). Unlike what has been described for hypothyroid patients, the basal TSH level in euthyroid amenorrhea patients was not affected by bromocriptine, and we found that bromocriptine has no effect on the TRH-TSH response.     

Apoptosis and antiphospholipid antibodies

This research examined the effect of peer support on breastfeeding duration and exclusivity (breastfeeding without supplements) in a population of low-income women during the first 3 months postpartum. Participants in the peer counselor group (n = 18) exhibited higher rates of exclusive breastfeeding across time than those without a counselor (n = 18), and more exclusive breastfeeding was associated with long duration overall. Mother's career plans had the greatest effect on duration of breastfeeding. Women who intended to return to work, attend school, or both breastfed 6 to 9 weeks less than participants who intended to stay home. Attendance at a breastfeeding class and knowing someone who had breastfed was significantly correlated with a longer duration of breastfeeding. Nutritionists from the Women, Infants and Children (WIC) Program were the primary source of breastfeeding information. Two main factors discouraged women from breastfeeding: returning to work, school, or both and the perception of a diminished milk supply. Greater emphasis should be placed on prenatal breastfeeding education for low-income women, and their mothers and grandmothers should be included. Peer support is one important component of social support in the area of breastfeeding that community health nurses (CHNs) can utilize. CHNs are in a unique position to assist working mothers, provide support, and develop educational programs to enhance breastfeeding success in this population.     

Antagonism of l-stepholidine against bromocriptine-inhibition on prolactin level in lactational rats

AIM: To study the antagonism of l-stepholidine (SPD) against bromocriptine (Bro)-inhibition on prolactin (PRL) level. METHODS: Bro (0.5 mg.kg-1.d-1, s.c.) reduced the PRL and caused a dysplasia of mammary gland in lactational rats. The weight growing of newborn rats was retarded. The PRL of the lactational rats was assessed by immunoradiometric assay (IRMA); the weight of newborn rats and development of mammary glands in lactational rats were also examined. Antagonism of SPD was evaluated. RESULTS: SPD (30 & 100 mg.kg-1.d-1, i.p.) obviously antagonized the Bro that induced lowering the PRL level in lactational rats, the PRL was 11 +/- 4 & 23 +/- 6 micrograms.L-1 (NS 7 +/- 2) respectively on d 15 of postpartum and the development of mammary gland in lactational rats was normal. The newborn rats grew rapidly in 11-15 d. CONCLUSION: SPD possessed an antagonism with Bro inhibition on D2 receptors located in the pituitary gland, and was an antagonist of dopamine D2 receptors.     

Postpartum amenorrhoea in Ethiopia: the role of weaning, child death, and socioeconomic factors

Using data from the 1990 National Family and Fertility Survey (NFFS) and employing discrete-time hazards models, we examine the effect of weaning, child death, and socioeconomic factors on postpartum amenorrhoea in Ethiopia. The results show that 91 in every 100 mothers breastfed their child for at least 6 months. The median duration of breastfeeding stands at 18 months, and amenorrhoea lasts for a median duration of 12 months. Significant variations in breastfeeding and amenorrhoea duration are also observed among the different categories of breastfeeding women. The median duration of breastfeeding for lactating women is 24 months, 6 months for those who weaned, and 2 months for those whose child died. The median duration of postpartum amenorrhoea is 14 months for breastfeeding women, 12 months for those who weaned, and 6 months for those whose child died. Discrete-time hazard models reveal that child death has the strongest effect on the resumption of menses. Net of other factors, the risk of returning to menses increased 3 times for mothers whose child died. The effect of child death, however, decreases over time. Weaning also has a significant positive effect; and, like child death, its effect diminishes as time passes. The study further shows significant differences in the risk of returning to postpartum menses by socioeconomic characteristics of the women, even though they are breastfeeding.     

Gender effect on beta-endorphin response to exercise

PURPOSE: Twelve healthy men (26.4 yr) and women (26.8 yr) were compared at rest and after cycling for 25 min at 60 and 80% VO2max to determine whether gender and menstrual cycle influenced circulating beta-endorphin concentration (BE). METHODS: VO2max was determined on a cycle ergometer, and subjects completed the exercise in a randomized order. Women were tested in both the luteal (L) and follicular (F) phases of their menstrual cycle, which was confirmed by their blood estrogen levels. All tests were conducted in the morning after a 30-min rest (12-h postabsorptive). An indwelling venous catheter placed in a forearm vein enabled blood sampling at rest, 25 min of cycling, and 25 min of recovery. RESULTS: Resting BE was similar for men before both 60 and 80% intensities of exercise, 5.27 +/- 0.43 and 5.30 +/- 0.33 pmol.mL-1, respectively. BE was not significantly changed at 60% VO2max (6.54 +/- 0.33 pmol.mL-1) but significantly increased at 80% VO2max (11.90 +/- 1.98 pmol.mL-1). Women tended to have slightly lower BE during the L compared with F, but this did not reach significance (L = 4.40 +/- 0.22, F = 4.73 +/- 0.30 pmol.mL-1). Cycling at 60% VO2max did not significantly increase BE in the L (5.41 +/- 0.42 pmol.mL-1) nor the F (5.35 +/- 0.40 pmol.mL-1). Cycling at 80% VO2max increased BE to a similar extent in both the L and F phase, respectively (10.44 and 10.96). Although the BE concentrations tended to be slightly lower in women compared with men at 80% VO2max, this did not reach statistical significance. CONCLUSIONS: These data suggest that women cycling at 80% VO2max will have a similar BE response to men independent of their menstrual cycle. BE in women at rest and who exercise at lower exercise intensities may have slightly lower BE levels then men independent of the time of the women's menstrual cycle.     

Factors associated with serum levels of estradiol and sex hormone-binding globulin among premenopausal Japanese women

We measured serum levels of estradiol (E(2)) and sex hormone-binding globulin (SHBG) among 50 healthy premenopausal Japanese women in 1994 in Gifu, Japan, to investigate the relationships between potential risk factors for breast cancer and hormone levels. Using a self-administered questionnaire, we collected data on body size, physical activity, and previous disease history, as well as menstrual and reproductive histories of the woman and her mother. Blood samples were drawn from each subject on the 11th and 22nd days of her menstrual cycle. Higher serum E(2) levels were observed for women with shorter menstrual cycles. Age as well as cycle length were included in the regression models to determine the associations between hormone levels and study variables. Body mass index (BMI) was inversely related to SHBG level measured at the 11th day of the cycle, after adjusting for age and cycle length (r = -0.33; p = 0. 03). Women born in spring/summer had higher levels of E(2) on the 22nd day (p = 0.07) and higher levels of SHBG on both the 11th and 22nd days of the cycle (p = 0.01 and p = 0.06, respectively) than those born in other seasons. Physical activity at 13-15 years of age was inversely related to E(2) level on the 11th day of the cycle after controlling for age, cycle length, BMI, and birth month (r = -0.35; p = 0.04).     

Serum prolactin levels in undernourished Indian lactating women

1. Serum prolactin (PRL) levels, both basal and post-suckling peak, were estimated in fifty-seven lactating women. 2. Basal PRL levels were significantly higher in all lactating women irrespective of the duration of lactation as compared to the levels in non-pregnant, non-lactating women. 3. There was significant positive correlation (r 0.69, P less than 0.001) between the basal PRL levels and the post-suckling peak values. 4. After 8 months of lactation, peak post-suckling, PRL levels were not significantly different from basal values. 5. Basal PRL levels were significantly lower (P less than 0.05) in mothers whose infants were being supplemented. 6. PRL levels were not related to the mother's nutritional status as determined by body-weight. 7. The findings suggest that high PRL levels during lactation prolong the duration of lactional amenorrhoea and hence the relative infertility.     

Uptake of contraception during postpartum amenorrhoea: understandings and preferences of poor, urban women in Bangladesh

In urban Bangladesh, as in many other settings, an immediate postpartum family planning strategy prevails, where providers seek to promote and provide contraception at 40-45 days following birth to women regardless of their breastfeeding or menstrual status. Despite such practices, the majority of women choose to delay the initiation of contraception until menses resumes, often several months after birth. The present paper seeks to explain this discrepancy by describing poor, urban women's understandings regarding the chances of conception and the risks associated with contraceptive use in the postpartum period. Findings from in-depth interviews reveal that the majority of women perceive no personal risk of pregnancy during amenorrhoea, though most do not recognise an association between this diminished risk of conception and breastfeeding. In addition, the data illustrate that women are primarily concerned with their own and their newly born child's health and well-being in the period following childbirth, both of which are perceived to be extremely vulnerable. These perceptions, plus an understanding that modern methods of contraception are "strong" and potentially damaging to the health, mean that the majority of women are reluctant to adopt family planning methods soon after birth, particularly during postpartum amenorrhoea. The paper advocates that, since breastfeeding affords good protection against pregnancy for six to nine months following birth, efforts should be made to actively incorporate lactational amenorrhoea into postpartum family planning strategies in Bangladesh. Recommendations are also made for ways in which women may be encouraged to adopt contraception during amenorrhoea beyond the period of high natural protection. The paper highlights the importance of taking the client's perspective into consideration in attempts to improve the quality and effectiveness of family planning programmes.     

Effect of prolactin suppression on gonadotrophic secretion in the puerperium

Serum levels of prolactin (PRL), FSH, LH and oestradiol-17 beta were determined by radioimmunoassay in 57 lactating women and in 20 women in whom lactation was inhibited by ergocryptine (CS-154). Women who breast fed their infants exhibited high PRL levels which abruptly declined within 48 h post-partum, and remained low for the duration of the study. Serum FSH was undetectable during the first week post-partum in lactating as well as in CB-154 treated women. Thereafter, lactating women showed increasing FSH levels which reached a maximum by the third week post-partum. These FSH values were higher in lactating women than in the CBS-154 treated group. In contrast, LH levels were higher in those women receiving CB-154. Serum oestradiol-17 beta remained in low levels throughout the study, and no difference was observed between the two groups of subjects. From these results it seems that: 1) inhibition of PRL secretion leads to a faster recovery of gonadotrophin secretion toward the "menstrual type", and 2) PRL suppression produces no effect on the ovarian oestrogen production.     

Bentall operation, total aortic replacement and mitral valve replacement for a young adult with Marfan syndrome: a case of three-staged operation

BACKGROUND: Early postpartum discharge of babies was gradually introduced in Sweden in the 1980s on ideological grounds, based on the premise that maternity wards were unnatural settings for mothers and babies and hampered breastfeeding. From about 1990, early discharge was used as a means to reduce costs. The purpose of this study was to examine if mandated early discharge at Central Hospital of Karlstad, Sweden, influenced subsequent breastfeeding. METHOD: Breastfeeding outcomes of infants up to six months of age of all births in 1993 (n = 3231) were compared with the outcome of newborns in 1990 (n = 1462). RESULTS: Breastfeeding at six months postpartum continued to increase during the early 1990s for both healthy and sick infants, irrespective of whether or not they were discharged early. In infants born in 1995 the breastfeeding rate at six months was 64 percent for healthy newborns and 53 percent for sick newborns. CONCLUSION: Factors other than the time of discharge, most likely a positive change of attitude in society and vigorous introduction of the Baby Friendly Hospital Initiative, seem to have been more important for successful breastfeeding.     

Predictors of patients remaining anovulatory during clomiphene citrate induction of ovulation in normogonadotropic oligoamenorrheic infertility

The diagnostic criteria used to identify patients suffering from polycystic ovary syndrome remain controversial. The present prospective longitudinal follow-up study was designed to identify whether certain criteria assessed during standardized initial screening could predict the response to ovulation induction with clomiphene citrate (CC) in 201 patients presenting with oligomenorrhea or amenorrhea and infertility. Serum FSH levels were within the normal range (1-10 IU/L), and all patients underwent spontaneous or progestin-induced withdrawal bleeding. Initial CC doses were 50 mg daily for 5 days starting on cycle day 3. In the case of an absent response, doses were increased to 100 and 150 mg daily in subsequent cycles. First ovulation with CC was used as the end point. After a complete follow-up (in the case of a nonresponse, at least 3 treatment cycles with daily CC doses up to 150 mg), 156 patients (78%) ovulated. The free androgen index (FAI = testosterone/sex hormone-binding globulin ratio), body mass index (BMI), cycle history (oligomenorrhea vs. amenorrhea), serum androgen (testosterone and/or androstenedione) levels, and mean ovarian volume assessed by transvaginal sonography were all significantly different (P < 0.01) in responders from those in nonresponders. FAI was chosen to be the best predictor in univariate analysis. The area under the receiver operating characteristics curve in a multivariate prediction model including FAI, BMI, cycle history, and mean ovarian volume was 0.82. Patients whose ovaries are less likely to respond to stimulation by FSH due to CC treatment can be predicted on the basis of initial screening characteristics, such as FAI, BMI, cycle history (oligomenorrhea or amenorrhea), and mean ovarian volume. These observations may add to ongoing discussion regarding etiological factors involved in ovarian dysfunction in these patients and classification of normogonadotropic anovulatory infertile women.     

The effect of LHRH and TRH on human interferon-gamma production in vivo and in vitro

Accumulating evidence suggests that hypothalamic luteinizing hormone-releasing hormone (LHRH) and thyrotropin-releasing hormone (TRH) are two hypophysiotropic factors which modulate the immune response. The aim of the present study was to determine the in vivo effects of an intravenous bolus of LHRH and TRH on plasma interferon (IFN)-gamma production in five normoprolactinemic women with irregular menstrual cycles. We also determined prolactin (PRL), thyrotropin (TSH), follicle stimulating hormone (FSH), and luteinizing hormone (LH) levels before and after intravenous administration of LHRH and TRH. The results demonstrate that intravenous bolus of LHRH/TRH increases plasma IFN-gamma levels, with the maximum response 45 min after in vivo administration of hypothalamic peptides and after peak levels of adenohypophyseal hormones (PRL: 15 min; TSH: 30 min; FSH: 30 min; LH: 30 min). In order to investigate a possible direct action of hypothalamic hormones on immune cells, we also evaluated, in the same subjects, the influence of LHRH and TRH on IFN-gamma production by human peripheral blood mononuclear cells (PBMCs), collected before the intravenous administration of the peptides and stimulated in vitro with bacterial superantigen staphylococcal enterotoxin A (SEA) and concanavalin A (Con A). LHRH and TRH, separately and together, significantly enhanced in vitro IFN-gamma production by SEA- and ConA-activated PBMCs. The present results suggest that hypothalamic peptides (LHRH and TRH) directly, and/or indirectly pituitary hormones (PRL, TSH, FSH, and LH) or IL-2, have stimulatory effect on IFN-gamma producing cells and are further evidence of interactions between the neuroendocrine and immune systems.     

Does alpha-melanocyte-stimulating hormone from the pars intermedia regulate suckling-induced prolactin release? Supportive evidence from morphological and functional studies

Recent evidence suggests that substances derived from the hypophyseal intermediate lobe (IL) play a crucial role in the regulation of suckling-induced PRL secretion. The purpose of the present study was to explore this possibility further by determining whether the suckling stimulus acutely increases the secretory activity of the IL and whether alpha MSH, a major secretory product of the IL, plays a specific role in suckling-induced PRL release. Light microscopic morphometric analysis of serial pituitary sections obtained from lactating rats revealed that as little as 1 min of suckling caused a significant increase in the proportion of the IL that was in secretory configuration (11.8 +/- 0.7% vs. 6.7 +/- 0.5%; 1-min suckled vs. nonsuckled control; mean +/- SE). Moreover, the fraction of the IL in secretory configuration continued to increase after 5 and 10 min of nursing (to 16.0 +/- 0.8% at 5 min and 18.2 +/- 0.7% at 10 min). In contrast, serum PRL was not significantly elevated above the control level after 1 min of suckling (18.1 +/- 13.5 vs. 9.9 +/- 6.5 ng/ml, 1-min suckled vs. control). In fact, a significant rise in PRL levels (to 314.4 +/- 19.4 ng/ml) could be detected only after 10 min of nursing. Thus, secretion by the IL in response to suckling preceded the release of adenohypophyseal PRL, suggesting that a secretory product(s) from the pars intermedia is involved in the modulation of nursing-induced PRL release. Having established a sequential temporal relationship between these two phenomena, we next investigated whether alpha MSH was the IL factor involved in the regulation of suckling-induced PRL secretion. To this end, lactating rats were injected either with antiserum to alpha MSH or preimmune serum and then allowed to nurse their pups. Serial blood samples were taken from the mothers 15, 30, 60, and 90 min after the litters were returned, and serum PRL was measured by RIA. We found that the suckling-induced rise in serum PRL was severely attenuated in animals that received anti-alpha MSH serum. This suppression was most evident at 15 min (70.1 +/- 13.4 vs. 323.5 +/- 127.0 ng/ml, antibody treated vs. preimmune serum control) and persisted throughout the entire 90-min test period. When taken together, our results suggest that suckling-induced PRL secretion is mediated at least in part by alpha MSH released from the hypophyseal IL.